Among the large, flat, full color, high-definition television screens or panels currently available, the gas-plasma-type panel has achieved considerable success. These display panels may be hung on a wall, much like a framed picture or the like, and provide excellent display quality, as well as a wide viewing angle. Screens as large as 55" diagonal size have been produced with a thickness of around 1/4 in. While these panels are quite light and thin, they can produce sharp pictures in rooms with only ordinary illumination.
The construction of these plasma display panels is rather complex, particularly in view of the large number of pixels that must be used to achieve the high-definition desired. The panels utilize a pair of parallel dielectric glass plates including a front plate and a rear plate. The plates are separated by a barrier rib structure that serves to define with the two glass plates, a plurality of pixels each of which generally includes 4 individual color subcells arranged in a square pattern. In a typical design, the 4 subcells include a blue subcell, a red subcell and 2 green subcells. Each subcell contains a color phosphor that is activated by an excited volume of gas plasma contained in the subcell. The gas plasma is excited by means of a voltage pulse generated by a control circuit.
The control circuit includes a plurality of electrodes including parallel conductive anode strips that are printed or formed by a thick film technique on the interior surface of the rear glass plate. Correspondingly, a plurality of parallel conductive cathode strips are printed or formed by a thick film technique on the interior surface of the front plate and oriented perpendicular to the anode strips on the rear plate.
A white backing layer is formed on the interior surface of the rear plate to provide a white backing for the phosphors. The individual phosphors for each cell are printed or formed by various other techniques on the white backing layer in a pattern that corresponds to the pattern of the color subcells.
The front plate also has a plurality of color filters in the form of film segments applied to the outer surface of the panel in a pattern corresponding to the arrangement of the color subcells. For example, a red filter segment is positioned over a subcell with a red phosphor, a blue filter segment is positioned over a subcell with a blue phosphor and a green filter segment is positioned over a subcell having a green phosphor. The remaining portions of the outer surface of the front plate have a black film layer applied thereto to form a black matrix that surrounds and encloses the filter segments.
The conventional technique for forming the barrier rib structure so as to partition the color subcells, has been to perform a number of screen prints having the desired barrier rib pattern thereon defined by a layer of fusible dielectric material such as a dielectric thick film material. The thickness of these individual prints may be for example, about 0.02 mm. The height of the color subcells may be for example, between 0.1 mm and 0.2 mm so that 5 or 10 or more individual screen prints would be required to produce the desired barrier rib height.
These multiple screen prints are placed or printed on the interior surface of one of the glass plates (preferably the rear plate) and aligned with one another as well as with the respective front glass plate. The assembly is then fired to fuse the screen patterns to one another and to the interior surfaces of the glass plates.
The accurate alignment of the successive prints and the line definition required over the relatively large area of the surface of the glass plates, are critical to the proper functioning of the plasma display panel. Because the alignment of each print is so critical, the process is quite cumbersome and also vulnerable to error.
The process of the present invention, however, reduces the difficulties indicated above and affords other features and advantages heretofore not obtainable.